Every summer fashionistas from Milan to Montauk gravitate to one "it" handbag, but this season three silhouettes—all from British design houses—are dominating the red-hot luxury leather-goods market. And they're not the usual logo-laden suspects.

Both Mulberry and Tanner Krolle, two classic English accessory houses, have undergone serious renovations in the past few years with new investors, creative directors and younger, hipper images. The result: celebrities and trendsetters like Julia Roberts, Scarlett Johansson and Victoria Beckham are snapping up their pretty pastel-colored totes, particularly the "Roxy" and "Queenie." Newer to the market is London-based designer Luella Bartley, whose...